1. Field of the Invention
The present invention relates to a three-dimensional measurement apparatus, a three-dimensional measurement method, and a storage medium.
2. Description of the Related Art
As a method for measuring the three-dimensional shape of an object to be measured from the principles of a triangulation method after the capture of an image of the object to be measured on which pattern light has been projected subsequent to the projection of the pattern light onto the object to be measured, there is a pattern projection method. Typical examples of a high-accuracy three-dimensional shape measurement technique using such a pattern projection method include a spatial encoding method, a phase-shift method, and an optical cutting method. However, with a spatial encoding method, for example, since plural stripe pattern light beams are projected onto an object to be measured in time series to capture its images, it takes time to three-dimensionally measure the object to be measured by the number of the captured images. With a phase-shift method as well, time is taken because plural images are captured in accordance with measurement regions. In an optical cutting method, the capture of many images is required because the capture is performed while scanning a region using line projection. To reduce measurement time even slightly, it has been considered that a technique of limiting a region(s) to be three-dimensionally measured is used.
As an example of such a conventional technique, there is a technique in which a relationship is stored that has been established between a region from which characteristics of an object to be measured that could be obtained from a two-dimensional image of the object to be measured to be extracted and a region to be three-dimensionally measured of the object to be measured, the characteristics of the component are extracted from the two-dimensional image at the time of its three-dimensional measurement, and the above three-dimensional measurement region is irradiated with light to obtain data on its three-dimensional shape (see Japanese Patent No. 3859571).
As an example of a conventional technique for effectively controlling pattern projection, there is a technique in which a pattern is projected onto an object to be measured first to capture an image of the object to be measured, and then the type and the number of patterns to be projected the second and subsequent times are determined by an optical spatial modulation element based on the amount of characteristics and the amount of a change(s) of the object to be measured in the captured image (see Japanese Patent Laid-Open No. 2006-292385).
In conventional pattern projection methods including the foregoing method, the effective use of three-dimensional shape data obtained in advance for the three-dimensional measurement of only a region(s) where such measurement is required is not made; therefore it is required that three-dimensional measurement be made of the whole object, and thus there is a need to make three-dimensional measurement at a region(s) where no change has occurred. Because of this, in cases where many images are captured and/or many pixels are used, it takes time to make three-dimensional measurement. In methods of limiting a measurement region from a two-dimensional image, it is required that a measurement system other than a three-dimensional measurement system be provided, and therefore a problem has arisen of a measuring system and a processing system becoming complicated.
In view of the above problem, the present invention provides a technique of making three-dimensional measurement at high speed through the effective use of three-dimensional shape data obtained in advance.